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Nitrogen Metabolism And Iron Reduction In Aquaspirillum Magnetotacticum (Nitrate, Fixation, Magnetic Bacterium), Dennis Alfred Bazylinski

Doctoral Dissertations

Aquaspirillum magnetotacticum strain MS-1 grew microaerobically but not anaerobically with NO(,3)('-) or NH(,4)('+) as the sole nitrogen source. Cell yields varied directly with NO(,3)('-) concentration under microaerobic conditions. Products of NO(,3)('-) reduction by growing cells included NH(,4)('+), N(,2)O, NO, and N(,2) but not NO(,2)('-) or NH(,2)OH. The inclusion of NH(,4)('+) in growth medium prevented NO(,3)('-) reduction to NH(,4)('+) but not to N(,2)O or N(,2). Cells consumed O(,2) while denitrifying and this appears to be the first described species with an absolute requirement for O(,2) while denitrifying.

Cultures grown with NO(,3)('-), in contrast to NH(,4)('+), contained fewer cells without magnetosomes. Moreover, …

Ecology Of Rocky Subtidal Communities: The Role Of Modiolus Modiolus (L) And The Influence Of Disturbance, Competition, And Mutualism, Jon Drew Witman

Doctoral Dissertations

This study presents an analysis of physical and biological processes regulating the structure of rocky subtidal communities off coastal New Hampshire and southern Maine, USA, with emphasis on the ecology of the horse mussel Modiolus modiolus (L.). Quantitative sampling and multivariate analysis revealed 3 communities: (1) Modiolus community; (2) 30 m community of species with highest densities outside mussel beds; (3) 8-18 m community of species with maximal densities outside mussel beds.

Controlled field experiments, a natural grazing experiment, and long-term photographic monitoring (5 yrs) enabled patterns of Modiolus community structure to be related to the processes maintaining them. Bivalve, …

Oogenesis In Tubularia Larynx And Tubularia Indivisa (Hydrozoa, Athecata), Barry W. Spracklin

Doctoral Dissertations

In Tubularia larynx and T. indivisa, interstitial cells proliferate in the ectoderm of the gonophore stalk and peduncle of the raceme and migrate in the endoderm to the apex of the young gonophore buds where they proliferate in the endoderm to form the entocodon and germ cell mass. Eggs are produced sequentially in the gonophores of both species. Each egg is the result of fusion of 1200-2000 cells interconnected by cytoplasmic bridges into a large complex. At the center of each complex are 15-18 morphologically similar cells, all of which begin meiosis and form germinal vesicles and are considered oocytes. …